A few days ago my Cloud Ultra dropped off of Site Manager, and all of the devices connected to it (that could) reported they were offline. The device is 2000 miles away from me.
I sent a friend in to look at it, and it seemed happy, but something was clearly up. Power cycling it and the ISP router (uses GPON fiber) didn't change a thing.
Reported the issue to the ISP automated system and within minutes everything came back, but it turned out the Cloud Ultra didn't think it had been offline for 3 days. It saw the brief loss of connection when it was power cycled, but everything else was green.
So how can the router think it is "connected" when Site Manager can't get to it and none of its connected devices can get to their "call home" services? DNS? Something else? (As it didn't realize it was disconnected, I never got a notification from Uni, I only noticed because of the other devices that failed to call home a timely fashion).
Source: r/Ubiquiti · by /u/controlav